Swimming Microbots

BBC has an article about swimming microbots that can swim through blood veins. Japanese
scientists have created a tiny screw mechanism that can spin for
swimming propulsion. These microbots can be injected into the body
with a
hypodermic needle and once inside a blood vein, the robot can be
steered with the aid of 3D magnetism field and controller in any
direction. The micro
swimming bots can deliver drugs to specific parts of the body, burrow
by screwing itself
into tumors in seconds or poke a hot spike into cancerous tissues to
kill them. They hope to create smaller versions that can get even into
the smaller blood veins of the brain.

Here's another article from NewScientist with pictures. Appears
it's not so much a robot as a screw with a magnet inside. I'd like to
see how the 3D magnetic controller works to make it spin and steer.